Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X03: Optics and Photonics in Polymers and Soft Matter II: PhotonicsFocus Live
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Sponsoring Units: DPOLY DSOFT DBIO DAMOP Chair: Danielle Mai, Stanford Univ; Chaitanya Ullal, Rensselaer Polytechnic Institute |
Friday, March 19, 2021 8:00AM - 8:12AM Live |
X03.00001: Color, structure, and rheology of a diblock bottlebrush copolymer solution Matthew Wade, Dylan J. Walsh, Ching-Wei Johnny Lee, Elizabeth Kelley, Kathleen Weigandt, Damien S. Guironnet, Simon Rogers A structure–property–process relation is established for a diblock bottlebrush copolymer solution, through a combination of rheo-neutron scattering, imaging, and rheological measurements. Polylactic acid-b-polystyrene diblock bottlebrush copolymers were dispersed in toluene with a concentration of 175 mg/mL, where they self-assembled into a lamellar phase.The solution color, as observed in reflection, is a function of the shear rate. Under equilibrium and near-equilibrium conditions, the solution has a green color. At low shear rates the solution remains green, while at intermediate rates the solution is cyan. At the highest rates applied the solution is indigo. The lamellar spacing is shown to be a decreasing function of shear rate, partially accounting for the color change. The intramolecular distance between bottlebrush polymers does not change with shear rate, although at high shear rates, the bottlebrush polymers are preferentially aligned in the vorticity direction within the lamellae. We therefore form a consistent relation between structure and function, spanning a wide range of length scales and shear rates. |
Friday, March 19, 2021 8:12AM - 8:24AM Live |
X03.00002: Investigating the trade-off between color saturation and angle-independence in photonic glasses Ming Xiao, Anna B. Stephenson, Victoria Hwang, Vinothan N Manoharan Photonic glasses, isotropic structures with short-range correlation, can produce structural colors when the wavelength of light is comparable to the correlation length. Experimental studies suggest it is difficult to obtain both highly saturated and angle-independent structural colors in photonic glasses without absorption. To understand why, we quantitatively analyze the trade-off between saturation and angle-dependence in photonic glasses. We take advantage of the isotropy, which allows us to express the degree of short-range order through the structure factor S(q). With this simplification, we are able to simulate multiple scattering using a Monte Carlo approach. We use the simulations to understand how varying the degree of short-range order affects the color. We show that both the color saturation and angle-independence depend primarily on the shape of the first peak of the structure factor. |
Friday, March 19, 2021 8:24AM - 8:36AM Live |
X03.00003: Combined electric and photocontrol of selective light reflection by oblique helicoidal cholesteric doped with azobenzene derivative Kamal Thapa, Olena Iadlovska, Hari Krishna Bisoyi, Daniel Paterson, John Storey, Corrie T. Imrie, Quan Li, Sergij V Shiyanovskii, O Lavrentovich A cholesteric liquid crystal (ChLC) composed of flexible dimeric molecules shows an oblique helicoidal state (ChOH) in the presence of an electric field. By controlling the ChOH pitch P by the electric field, one can shift the wavelength of the selective reflection (transmission) of light in a broad spectral range, from UV to IR. In this work, we demonstrate that a combined action of the electric field and UV irradiation could continuously tune the pitch of a ChOH material doped with photosensitive azobenzene molecules capable of trans-cis isomerization. At a fixed voltage, UV irradiation causes a gradual redshift of the reflection wavelength by about 100 nm for the explored composition. The dynamic scenarios of the radiation-induced changes are described by kinetic equations. The phenomenon can find applications such as smart windows, lasers, optical filters, and sensors of UV intensities/doses. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X03.00004: Bragg diffraction of obliquely incident light at heliconical cholesteric structures Olena Iadlovska, Mateusz Mrukiewicz, Sergij V Shiyanovskii, O Lavrentovich An electric field acting on a chiral mixture of flexible dimers produces an oblique helicoidal (also called heliconical) cholesteric (ChOH) state with its axis parallel to the field (Xiang, J. et.al, Phys. Rev. Lett. 112, 217801 (2014); Xiang, J. et.al, Adv. Mater. 27, 3014 (2015)). Both the ChOH period and the conical angle depend on the applied field, which enables electrically tunable Bragg diffraction in a broad spectral range from ultraviolet to infrared. We demonstrate experimentally that oblique propagation of light results in reflection at both the half- and full pitch of the ChOH structure. Diffraction at the half-pitch periodicity shows bandgap triplets whose lateral peaks are polarization dependent, while the central peak is not. The full pitch bandgap is a singlet characterized by a wide bandwidth and total reflection at a large angle of oblique incidence and whose polarization characteristics are similar to those of the central peak of the half-pitch triplet. We develop a model of light propagation in ChOH that explains and reproduces the observed optical effects at oblique incidence of light that might be attractive for applications such as electrically tunable band-pass filters, mirrors, low-threshold lasers, etc. The work is supported by NSF grant ECCS-1906104. |
Friday, March 19, 2021 8:48AM - 9:00AM Live |
X03.00005: Easy to pattern, chemically resistant 1-dimensional polymer photonics Mark Robertson, Zhe Qiang 1-dimensional photonic crystals (PCs) reflect certain wavelengths of light using periodic dielectric layers with mismatched refractive indices. Many polymer and inorganic systems exist for fabricating PCs, but challenges remain to create a PC that is stable under harsh chemical conditions. Furthermore, patterning PCs to provide spatial control of reflected light often requires complex or tedious processing steps. Herein, we demonstrate a relatively simple and scalable approach to fabricate chemically resistant PCs from cheap commercially available materials, poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) and phenolic resin (resol), using dip-coating to tune the λmax of the PC by adjusting the substrate moving velocity. The layers have a naturally high refractive index contrast (Δn≈0.3) and are able to exhibit high stability when exposed to various organic solvents, acid and base aqueous solutions. Moreover, an easy-to-pattern approach is offered by using a PDMS pad to spatially control the hydrophobicity of PVDF-CTFE and direct the deposition of resol layer. We believe this work provides a facile approach for patterned PCs with tunable reflecting behavior and excellent chemical stability. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X03.00006: Responsive Polyelectrolyte Multilayer Cladding for Reversibly Programmable Photonics Christian Sproncken, Mahir Mohammed, Berta Gumí-Audenis, Emilija Lazdanaité, Ripalta Stabile, Oded Raz, Ilja Voets Polyelectrolyte multilayers (PEMs) are versatile, easily applied thin films, which respond to various triggers such as salt concentration or pH, leading to morphological changes in the polymer network. Aiming to use PEMs to program photonic circuits, we prepare the multilayers on model substrates by alternatingly depositing poly(allylamine hydrochloride) and poly(acrylic acid). These PAH/PAA PEMs reversibly swell upon treatment with acidic (pH = 2) and near-neutral (pH = 5.5) solutions. Interestingly, drying from these discrete pH values generates PEMs with low or high porosity and thus, contrasting refractive indices. Next, we demonstrate that the refractive index change between the distinct states of the PEM alters the response of the underlying photonic devices. We present two approaches to control this shift of the device output. The first requires a thin layer of silica, applied between the device and the PEM, while the second method involves area-selective deposition of the PEM on parts of the device. Each of these allows us to reversibly program the device response, without requiring continuous input, paving the way for the much desired programmability of photonic integrated circuits. |
Friday, March 19, 2021 9:12AM - 9:48AM Live |
X03.00007: Self-Assembly of Colloidal Diamond Invited Speaker: David Pine Self-assembling colloidal cubic diamond been a longstanding goal because of its potential for making materials with a photonic band gap. These materials suppress spontaneous emission and have applications in micro photonics such as optical waveguides, filters, and laser resonators. Cubic diamond s preferred over more easily self-assembled structures such as face-centered cubic (FCC) because diamond has a much wider band gap and is less sensitive to imperfections. The band gap in diamond crystals opens up for a refractive index contrast of about 2.0, which means that a photonic band gap could be achieved using known materials at optical frequencies, which appears not to be possible for FCC crystals. Nevertheless, self-assembled colloidal diamond has not previously been realized. Because particles in a diamond lattice are tetrahedrally coordinated, one approach has been to self-assemble spherical particles with tetrahedral sticky patches. Difficulties persist, however, because patchy spheres possess no mechanism to select the proper staggered orientation of tetrahedral bonds on nearest-neighbor particles, a requirement for cubic diamond. We show that by synthesizing partially compressed tetrahedral clusters with retracted sticky patches, colloidal cubic diamond can be self-assembled using patch-patch adhesion in combination with a steric interlock mechanism that selects the proper staggered bond orientation. Colloidal particles in the self-assembled cubic diamond structure are highly constrained and mechanically stable, which make it possible to dry the suspension and retain the diamond structure. This makes these structures suitable as templates for forming high-dielectric-contrast photonic crystals with cubic diamond symmetry. Photonic band structure calculations reveal that the direct and inverse lattices exhibit promising optical properties, including a wide complete photonic band gap. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X03.00008: Waveguide Encoded Lattices (wels): slim polymer films with enhanced fields of view inspired by arthropodal compound eyes. Kathryn Benincasa, Kalaichelvi Saravanamuttu, Cecile Fradin In this presentation, we will describe a family of 2 mm to 3 mm thick, polymer films inscribed with WELs, which - like arthropodal compound eyes - have enhanced panoramic field of view (FOV). [1-3] These include an exceptionally high density of light harvesting waveguide units (>15,000 cm-2), excellent imaging resolution, infinite depth of field and operability at all visible wavelengths including broad incandescent spectra (like sunlight) and discrete spectral ranges of lasers and LEDs. WELs transmit, focus and invert images without need for bulky optics and conversely, control the shape and trajectory of light beams. Different from the curved architectures of compound eyes, WELs are plane-faced, optically flat, slim films, which due to their translational symmetry could be extended over large areas (e.g. through roll-to-roll manufacturing) and due to their flexibility, integrated with ease into technologies such as LCDs, solar cells, cameras and smart phones. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X03.00009: Electrodynamic modeling of leafhopper brochosomes for synthetic antireflective coatings Progna Banerjee, Gabriel R. Burks, Sarah B. Bialik, Elizabeth Bello, Marianne Alleyne, Jeffrey E. Barrick, Charles M Schroeder, Delia Milliron Insect-inspired materials hold strong promise to solve many global challenges and applied in functional materials including adhesives, sensors, actuators, hydrophobic and optically active surfaces. There still exists a knowledge gap in designing and developing nature-based materials. Leafhopper (Hemiptera, Cicadellidae) secreted brochosomes, hollow buckyball-like multifunctional nanostructures, are a promising material relevant for the development of synthetic coatings with antireflective and hydrophobic behavior. Using electrodynamic near-field modeling simulations, we study the optical properties by varying the brochosome geometry, arrangements (ordered/disordered with different packing fractions), material properties, and leafhopper species. Simulations are used to model scenarios where the pits are filled in with different materials, directing the design of new non-natural hypothetical structures not evolved by leafhoppers. Experiments with purified brochosomes are used to determine various optical parameters, and compared to simulations, with the results being indicative of the rearrangements in spatial electric field distribution in the spectral regime being tied to the geometric configurations in these brochosomes. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X03.00010: Chiral Liquid Crystal Lenses Confined in Microchannels Sean Hare, Beatrice E Lunsford-Poe, MinSu Kim, Francesca Serra It is known that the liquid crystalline smectic-A phase has geometric defects, called focal conic domains, which can be used as gradient-index lenses. Cholesteric (chiral nematic) phases also have circular topological defects that form lenses tunable with temperature. We have explored a weakly chiral system in which both types of defects can be present in the same material at different temperatures, and demonstrated a strategy for creating tunable lenses whose focal length can be changed with temperature. To study this behavior, we have confined liquid crystal in microchannels and measured the focal length of the lensing defects and their behavior near the phase transition. We have determined the carefully controlled experimental conditions that make the simultaneous presence of smectic focal conic domains and the circular cholesteric domains possible, such as the concentration of chiral dopant and the rate of heating and cooling. The transformation of focal conic domains into circular cholesteric domains is a new example of memory at the phase transition between smectic-A and nematic liquid crystals. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X03.00011: Thermal-Responsive Second Harmonic Generation in Poly(Ethylene Oxide)/Chromophore Crystalline Films Yifan Xu, Rui Zu, Rachel Martin, Venkatraman Gopalan, Robert Hickey Amorphous, high-glass transition temperature polymer materials containing electric-field-poled nonlinear optical (NLO) chromophores have shown promise in optical information processing applications. A major hurdle in using hybrid polymer/NLO chromophore materials is that the chromophore orientation will randomize over time, drastically impairing and reducing widespread use. Here, we present that films composed of poly(ethylene oxide)/ 2-chloro-4-nitroaniline (PEO/CNA) host-guest crystalline complexes exhibit stable and long-term second harmonic generation (SHG) activity, which is a result of the alignment of chromophore molecules during film crystallization. Differential scanning calorimetry (DSC) and grazing incidence wide-angle X-ray scattering (GIWAXS) confirmed the formation of the crystalline complex structure. SHG results indicate the non-centrosymmetric structure in PEO/CNA crystalline complex, and SHG intensity is maintained while at room temperature for weeks. Furthermore, the hybrid films exhibit thermal-responsive SHG activity in which SHG intensity sharply decreases as the melting temperature of the film is approached due to the phase transition from a crystalline to a liquid state. |
Friday, March 19, 2021 10:36AM - 10:48AM Live |
X03.00012: Transient Laser Heating Enabled Nanocomposite Structures from Block Copolymers toward Photonic & Phononic Quantum Materials Fei Yu, Qi Zhang, Ulrich Wiesner Organic amphiphilic block copolymers swelled by carbon precursors self-assemble into a cocontinuous network mesophase via solvent vapor annealing. After carbonization in an inert atmosphere, the resulting mesoporous resin/carbon thin films are backfilled with amorphous silicon, acting as templates. The thermal stability of the templates derived from polymers is significantly enhanced via nanosecond transient laser heating to allow the crystallization of Si (temperatures upward of 1400 °C). Melting and recrystallization of Si during this highly non-equilibrium ultrafast time frame enable conformal template backfilling and the polycrystalline silicon inherits the mesostructural order of the 3D resin/carbon templates. Detailed analysis of X-ray scattering data reveals symmetry reduction from cubic alternating gyroids to orthorhombic networks with D2 point group symmetry. Such unique nanostructures from block copolymers obtained under non-equilibrium laser heating conditions could pave the way to topological photonic and phononic metamaterials in this growing field of soft matter enabled quantum materials. |
Friday, March 19, 2021 10:48AM - 11:00AM Live |
X03.00013: A Soft Photopolymer Cuboid That Computes with Binary Strings of Light Alexander D. Hudson, Matthew R. Ponte, Fariha Mahmood, Thomas Pena Ventura, Kalaichelvi Saravanamuttu Stimuli-responsive materials that compute represent a new way of using the diverse capabilities of polymeric systems – exploiting chemical changes to create functional structures that receive, process, and respond to information that enters the system in the form of a stimulus. In this presentation, we discuss a polymer with a nonlinear optical response – namely, a light-induced increase in refractive index – and describe how this response can form the basis of computing-inspired functions. The photopolymerizable cuboid performs three computing operations: data recognition and transfer; volumetric encoding, and binary arithmetic. Binary data, input in the form of three broad, mutually orthogonal beams of white light patterned with light (1) and dark (0) stripes, elicits the formation of up to three populations of filaments or waveguides within volume subdivisions (voxels) of the cuboid. Spontaneous self-organization of orthogonal waveguide populations yields ordered configurations that may be read at the sample output to perform operations. |
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